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There is a warning about consuming shellfish by the B.C. Centre for Disease Control, but there are still plenty of good ones such as these West Coast Mussels.

Photograph by: Kim Stallknecht
, PNG

The B.C. Centre for Disease Control is warning doctors that shellfish poisoning may be related to both commercial and self-harvested products.

During the past three years, three significant outbreaks of illness affecting 102 people were traced back to commercially harvested mussels and oysters from government-approved sites, according to an article in the summer edition of the British Columbia Medical Journal.

Four cases of paralytic shellfish poisoning were reported by doctors in 2012, and 62 cases of diarrhetic shellfish poisoning in 2011, the first recorded cases in B.C. All of the illnesses were traced to commercial shellfish harvested from government-approved locations.

Diarrhetic shellfish poisoning is characterized by extreme gastric distress, beginning within hours of eating tainted food and lasting about one day. Paralytic poisoning is caused by a neurotoxin stored by shellfish after an algae bloom. Symptoms begin soon after eating and may include diarrhea and vomiting as well as tingling of the lips, tongue, arms and legs, as well as shortness of breath.

Algae blooms known as red tide are a common cause of both these syndromes.

In addition to the cases of shellfish poisoning detailed in the journal article, an outbreak of norovirus that sickened 36 people in 2010 was linked to an incident in which a harvester allegedly vomited into the water in the harvest area, said co-author Tom Kosatsky, the medical director of environmental health services for the BCCDC.

“That was certainly something that shouldn’t have happened. But it can happen, and it shows you how little material can lead to an outbreak of Norwalk virus,” said Kosatsky. “The ocean is big, vomit is little, so it doesn’t take much virus to induce illness.”

Shellfish are filter feeders that concentrate whatever pathogens are present in the water, he said.

“For the most part, these outbreaks came from areas that were regulated and operated relatively properly,” Kosatsky said.

Physicians are a vital part of the system of oversight — a regime that includes water and product testing by harvesters and government bodies such as the Canadian Food Inspection Agency, the Department of Fisheries and Oceans, and Environment Canada — that limits the spread of illness.

While recent data does not suggest an increase in shell-related illnesses, the BCCDC wants to disabuse doctors of the widely held belief that self-harvesters who collect shellfish from closed or dangerous areas are the source of most cases of sickness, he said.

“Even under the best regulatory framework, there can be (outbreaks). Even where the beds are well-maintained and there is oversight by Fisheries and Oceans and product is tested regularly, you can still have problems,” he explained.

Physicians need to document and report suspected cases, and whenever possible obtain samples of the food so that it can be tested and recalled. Warnings also need to be issued in order to prevent illness in others, the article says.

Kosatsky characterized the risk associated with eating shellfish as similar to the risk of illness from eating ground beef.

Albion Fisheries director of quality assurance Musleh Uddin said the risk of illness from eating shellfish is lower than many other common proteins, and that the level of scrutiny on shellfish from government regulators is more stringent than on any other food on the market.

“If we have the original shellfish tags, that means that if we know someone is ill, we will know when and where it was harvested and distributed in less than an hour,” said Uddin.